Projecting Trump's been an interesting topic because Trump's rise in popularity was so unexpected by most observers, leading people to second-guess their normal prediction methods. By contrast, the Clinton-vs.-Sanders race was pretty plainly predictable.

In this post, Silver discusses his thoughts on projecting Trump's performance.

We can think of a few basic approaches. One of them is to assert that precedent doesn’t apply to this election and that Trump’s case is sui generis. It’s not clear where that leads you, however.

If Trump is “unpredictable,” a phrase we heard used to describe him so often during the primaries, does that mean his chances of defeating Hillary Clinton are 50/50? If that’s what you think, you have the opportunity to make a highly profitable wager. Betting markets put Trump’s chances at only 20 percent to 25 percent instead.

In fact, despite (or perhaps because of) the unusual nature of his candidacy, the conventional wisdom holds that Trump is a fairly substantial underdog. In contrast to 2012, when there were frequent arguments over how solid President Obama’s lead in the polls was, there hasn’t been much of a conflict between “data journalists” and “traditional journalists” on this question of Trump’s chances. Nor has there been one between professionals who cover the campaign and the public; most experts expect Trump to lose, but so do most voters.

But should this seeming consensus give us more confidence — or make us nervous that we’re underestimating Trump again?

Giving Trump a 20 percent or 25 percent chance of becoming president means that Clinton has a 75 percent to 80 percent chance. That might seem generous given that, under ordinary circumstances, the background conditions of this election (no incumbent running and a mediocre economy) would seem to suggest a tossup. Are Clinton’s high odds justified on the basis of the polls? Or do they require making heroic assumptions about Trump, the same ones that got everyone, emphatically including yours truly, in trouble during the primaries?

The short answer is that 20 percent or 25 percent is a pretty reasonable estimate of Trump’s chances based on the polls and other empirical evidence. In fact, that’s quite close to where FiveThirtyEight’s statistical models, which are launching today, have the race. Our polls-only model has Trump with a 19 percent chance of beating Clinton as of early Wednesday afternoon. (The forecasts will continually update as new polls are added.) Our polls-plus model, which considers economic conditions along with the polls, is more optimistic about Trump, giving him a 26 percent chance.

Part of me hopes that Johnson's chances will rise to be non-negligible; half because I like the Libertarian party and half because I want to see the projection website use a ternary plot instead of a stacked horizontal bar graph.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

Yeah, polls can be skewed in various ways. Though just to clarify, the above projections are from a high-performing data scientist's modeling. This modeling incorporates tons of surveys, plus other data sources, to make a well-educated projection.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

I just wonder how much of this is prediction and how much of this is self fulfilled prophecy? There have been several instances during Sanders v Clinton where his interpretations just blatantly support Clinton. They main stream media loves this guy because they are all pulling for the same cause. Sorry but a prediction that Trump has a 20% chance at this stage is completely meaningless, short of easing the minds of Clinton supporters.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

Sanders lost pretty early on. But among the mainstream media's biases, sensationalism is one of the strongest; the dry, by-the-numbers affair that the Democratic primary proved to be doesn't get clicks, so the media didn't objectively report how futile the Sanders campaign was. And it made them money, because the reporters peddling those stories got more clicks than those who didn't.

That said, you're probably right that the 80% odds on Clinton vs. 20% on Trump may not mean a lot to people, in the same sense that most people don't really even need to know who the current President is. Unless you're heavily involved in politics and need to make plans based on the upcoming election results, odds in general - or even the outcome - are probably little more than entertainment.

Still, even if your decision-making won't be seriously affected by the outcome - making the odds moot - the modeling techniques used to generate those odds are still really interesting since these techniques apply broadly across all of Science. For example, we commonly use the same modeling tricks in interpreting process data from chemical plants to control and optimize them, while the ads on this site are fed through Google's own data science algorithms to determine what content to show you.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

Sanders lost pretty early on. But among the mainstream media's biases, sensationalism is one of the strongest; the dry, by-the-numbers affair that the Democratic primary proved to be doesn't get clicks, so the media didn't objectively report how futile the Sanders campaign was. And it made them money, because the reporters peddling those stories got more clicks than those who didn't.

That said, you're probably right that the 80% odds on Clinton vs. 20% on Trump may not mean a lot to people, in the same sense that most people don't really even need to know who the current President is. Unless you're heavily involved in politics and need to make plans based on the upcoming election results, odds in general - or even the outcome - are probably little more than entertainment.

Still, even if your decision-making won't be seriously affected by the outcome - making the odds moot - the modeling techniques used to generate those odds are still really interesting since these techniques apply broadly across all of Science. For example, we commonly use the same modeling tricks in interpreting process data from chemical plants to control and optimize them, while the ads on this site are fed through Google's own data science algorithms to determine what content to show you.

I do not agree that the democratic primary was over early. I also do not wish to be dragged into analyzing Nate Silver's work. I've done it before and saw flaws and I don't want to waste anymore time on this guy. As far as Google's algorithms, I mostly just get shown websites I've visited before. You enjoy his work so let's just leave it there. My frustrations are really more of just how complacent everyone is with the state of journalism in this country right now.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

SciameriKen » Wed Jun 29, 2016 10:12 pm wrote:I just wonder how much of this is prediction and how much of this is self fulfilled prophecy? There have been several instances during Sanders v Clinton where his interpretations just blatantly support Clinton. They main stream media loves this guy because they are all pulling for the same cause. Sorry but a prediction that Trump has a 20% chance at this stage is completely meaningless, short of easing the minds of Clinton supporters.

This was in part, my point. The polls may be accurate or not, and they may be skewed by bias on purpose or not on purpose. The fact is, polls can influence the behavior of the electorate. Polls can also be manipulated. We can maybe wonder how much manipulation gets applied in the hope of directing the outcome of a vote.

Other than for conversation, polls are meaningless. The only thing they may do is motivate one side, or both sides to greater effort and activities. And they don't even have to be accurate to do that.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

SciameriKen » July 25th, 2016, 1:54 pm wrote:Now Nate is saying Trump would win if the election were held today. Long term he still believes Hillary will win - but was all this in his "20 percent chance" claim just under a month ago?

That's a fascinating question! As you note, Clinton had about 80% odds just two weeks ago, but now the odds slightly favor Trump.

Part of this is an expected consequence of the GOP National Convention coming a little before the DNC National Convention. As Silver had posted in his methodology page, they figure that the conventions may affect the statistics something like this:

.

This is, we knew that Trump would enjoy a transient advantage between the national conventions; it may reverse following the current DNC National Convention (July 25-28). Or, the DNC convention may go poorly; some commentators suggest that it's off to a rough start, e.g.:

Still, it does seem like there's some pro-Trump factor not captured by the models. While we knew Trump would get a temporary boost around the conventions, there may be other factors at play. For example, the recent pro-Trump trend started about 5 days before his convention started; this may've been due to preemptive media reporting on the topic or something like that, but it's unsatisfying to accept such speculation without supporting evidence.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

SciameriKen » July 25th, 2016, 1:54 pm wrote:Now Nate is saying Trump would win if the election were held today. Long term he still believes Hillary will win - but was all this in his "20 percent chance" claim just under a month ago?

That's a fascinating question! As you note, Clinton had about 80% odds just two weeks ago, but now the odds slightly favor Trump.

Part of this is an expected consequence of the GOP National Convention coming a little before the DNC National Convention. As Silver had posted in his methodology page, they figure that the conventions may affect the statistics something like this:

This is, we knew that Trump would enjoy a transient advantage between the national conventions; it may reverse following the current DNC National Convention (July 25-28). Or, the DNC convention may go poorly; some commentators suggest that it's off to a rough start, e.g.:

Still, it does seem like there's some pro-Trump factor not captured by the models. While we knew Trump would get a temporary boost around the conventions, there may be other factors at play. For example, the recent pro-Trump trend started about 5 days before his convention started; this may've been due to preemptive media reporting on the topic or something like that, but it's unsatisfying to accept such speculation without supporting evidence.

Well I think that is quite clearly the conclusion of the FBI case and the recent divulging of DNC emails. As bad as June was for Trump, July is nearly there for Clinton. These candidates have to learn to race to the top, not the bottom.

Re: Donald Trump Has A 20 Percent Chance Of Becoming Preside

SciameriKen » Wed Jun 29, 2016 10:12 pm wrote:I just wonder how much of this is prediction and how much of this is self fulfilled prophecy? There have been several instances during Sanders v Clinton where his interpretations just blatantly support Clinton. They main stream media loves this guy because they are all pulling for the same cause. Sorry but a prediction that Trump has a 20% chance at this stage is completely meaningless, short of easing the minds of Clinton supporters.

This was in part, my point. The polls may be accurate or not, and they may be skewed by bias on purpose or not on purpose. The fact is, polls can influence the behavior of the electorate. Polls can also be manipulated. We can maybe wonder how much manipulation gets applied in the hope of directing the outcome of a vote.

Other than for conversation, polls are meaningless. The only thing they may do is motivate one side, or both sides to greater effort and activities. And they don't even have to be accurate to do that.

We can maybe wonder how much manipulation gets applied in the hope of directing the outcome of a vote. Or maybe we don't have to wonder.